Arsenophosphomolybdic acid catalyst compositions and process for their preparation



United States Patent Ofice 3,379,652 Patented Apr. 23, 1968 3,379,652ARSENOPHOSPHOMOLYBDIC ACID CATALYST COMPOSITIONS AND PRQCESS FOR THEIRPREPARATION Howard S. Young, Kingsport, Tenn., assignor to Eastman KodakCompany, Rochester, N.Y., a corporation of New Jersey No Drawing.Continuation of application Ser. No. 316,543, Oct. 16, 1963. Thisapplication Apr. 28, 1967, Ser. No. 634,772

10 Claims. (Cl. 252-437) This application is a continuation ofapplication Ser. No. 316,543, filed Oct. 16, 1963, now abandoned.

This invention relates to new catalyst compositions and to theirmanufacture. More particularly the invention relates to newarsenophosphomolybic acid catalyst compositions and to a process fortheir preparation.

The arsenophosphomolybdic acid catalyst compositions of the inventionare valuable catalysts, for example, for the manufacture ofacrylonitrile by reaction between propylene, ammonia and molecularoxygen in the vapor phase at an elevated temperature, the manufacture ofacrolein and acrylic acid by reaction between propylene and molecularoxygen in the vapor phase at an elevated temperature and the manufactureof methacrolein and methacrylic acid by reaction between isobutylene andmolecular oxygen in the vapor phase at an elevated temperature.

The arsenophosphomolybdic acid catalyst compositions of the inventioncomprise a mixture of an oxide of arsenic and a phosphomolybdic acid.

In accordance with the process of the invention an intimate mixture of aphosphomolybdic acid, such as, for example, dodecamolybdophosphoricacid, and an oxide of arsenic such as arsenous oxide (As O or arsenicoxide (AS205) or mixtures thereof, is prepared and calcined. Thecalcination can be carried out, for example, by heating the catalystmixture at a temperature of from about 200 C. to about 600 C., usuallyfor a period of several hours or more. While it is preferred to carryout the calcining operation at a temperature of from about 200 C. toabout 600 C., higher or lower temperatures can be employed. The calcinedmixture is then reduced to operable granules or particles of any desiredsize. Preferably the calcining operation is carried out in the presenceof air or other suitable oxygen-containing gaseous mixture. However, itcan be conducted in the absence of oxygen.

Dodecamolybdophosphoric acid has the empirical formula: H PMo O Thecommercially available dodecamolybdophosphoric acid contains aboutthirty moles of water as hydrate per mole of acid.

The concentration of the dodecamolybdophosphoric acid can vary from 5 to60% by weight of the catalyst. The concentration of the oxide ofarsenic, calculated as AS205, can range from 1 to 20% by weight of thecatalyst. The catalyst compositions are ordinarily supported on acarrier. The percentages just given are for calcined carrier supportedcatalyst. Thus, the weight of the catalyst includes the weight of thecarrier.

Advantageously, the catalyst compositions are supported on a carriersuch as silica or silica gel, alumina, silicaalumina, kieselguhr,pumice, titania, zirconia, magnesia, clay, etc. The catalystcompositions can be readily regenerated by treatment with air or a gascontaining molecular oxygen at an elevated temperature. The regenerationcan be carried out, for example, at the temperature of the reaction inwhich the catalyst is employed or at a temperature higher than thereaction temperature.

The use of the catalyst compositions of the invention to prepareacrolein and acrylic acid by reaction between propylene and molecularoxygen in the vapor phase at an elevated temperature of from about 300C. to about 600 C., preferably from 350 C.-550 C., or methacrolein andmethyacrylic acid by reaction between isobutylene and molecular oxygenin the vapor phase at an elevated temperature of from about 300 C. toabout 600 C., preferably from 350 C550 C. is described and claimed incopending Young and McDaniel application Ser. No. 316,523, filed Oct.16, 1963, now abandoned.

The use of the catalyst compositions of the invention to prepareacrylonitrile by reaction between propylene, ammonia and molecularoxygen in the vapor phase at an elevated temperature is described andclaimed in copending Young and McDaniel application Ser. No. 509,459,filed Sept. 30, 1965, now US, Patent No. 3,287,394, as a division ofYoung and McDaniel application Ser. No. 364,834 filed May 4, 1964, nowU.S. Patent No. 3,321,411.

Any of the conventional types of apparatus suitable for preparingacrylonitrile by reaction between propylene, ammonia and molecularoxygen in the vapor phase at an elevated temperature or for preparingacrolein and acrylic acid from propylene and molecular oxygen in thevapor phase at an elevated temperature or for preparing methacrolein andmethacrylic acid from isobutylene and molecular oxygen in the vaporphase at elevated temperature can be employed in conjunction with thenew catalyst compositions of the invention. For example, a tubular typeof fluidized or fixed bed reactor or furnace which can be operated incontinuous or intermittent manner and which is equipped to contain thecatalyst in intimate contact with the entering feed gases can beemployed. The effluent gases are then conducted to suitable condensingand separatory equipment for recovering the desired reaction products.

The definitions of certain terms used in the examples are as follows:

Contact time is the average time in seconds which the reactants spend atreaction conditions in a volume equal to that of the catalyst bed.

The percent conversion of propylene to acrolein:

moles of acrolein formed moles of propylene fed X The percent yield ofacrolein:

moles of acrolein formed moles of propylene consumed X 100 The percentconversion of propylene to organic acids:

moles acrylonitrile formed moles propylene fed X 100 Based on ammonia,percent conversion:

moles acrylonitrile formed X 100 moles ammonia fed The yield may becalculated based on propylene or ammonia. Based on propylene, percentyield:

moles aorylonitrile formed 100 moles propylene consumed Based onammonia, percent yield:-

moles aerylonitrile formed X 100 moles ammoma consumed Gaseous hourlyspace velocity (GHSV) is defined as the number of volumes of feed gasesat standard temperature and pressure (STP) which pass through one volumeof catalyst bed in one hour.

This invention is further illustrated by the following examples ofpreferred embodiments thereof although it will be understood that theseexamples are included primarily for purposes of illustration and are notintended to limit the scope of the invention unless otherwisespecifioally indicated:

Example 1 A catalyst comprising 2.7% arsenic oxide and 42.8%dodecamolybdophosphoric acid on silica was prepared by adding a solutionof 252 g. dodecamolybdophosphoric acid hydrate in 150 ml. of water to825 g. of ammoniastabilized silica sol (30% silica), followed by theaddition of a solution of 12.2 g. of arsenic oxide in 100 ml. water. Thepreparation was heated with mechanical stirring until it thickened to ayellow slurry. It was dried on a steam bath and then calcined at 200 C.for four hours.

The catalyst was pulverized, sieved, and 200 ml. of 40 x 100 meshcatalyst material was charged to a reactor. A stream of 214 ml.propylene, 1071 ml. air, and 214 ml. water vapor per minute, STP, wascharged to the reactor. Reaction temperature was 475 C., with a contacttime of 2.9 seconds. Over a period of 30 minutes, 1.0 g. of acrolein wasrecovered, corresponding to a conversion of 6.4%, with a yield of 11.6%.Some acrylic acid was also formed during the reaction.

Example 2 A cut was made over the same catalyst in which no water wascharged to the reactor. The water vapor of the preceding example wasreplaced with an equal volume of nitrogen, so that the other conditionsremained the same. Over 30 minutes of operation, 1.1 g. of aorolein wasobtained, corresponding to a conversion to acnolein of 6.6%, with theyield 10.0%. Some acrylic acid was also formed during the reaction.

Example 3 A catalyst comprising 5.2% arsenic oxide and 41.6%dodecamolybdophosphoric acid on silica was prepared as describedhereinafter. 252 g. of dodecamolybdop'hosphoric acid hydrate wasdissolved in 150 ml. of water and concentrated nitric acid was addeduntil the green colored solution turned to yellow. The solution justprepared was added to 825 g. of ammoniastabilized silica sol (30%silica) and the resulting solution was heated nearly to boiling and thena solution of 24.5 g. of arsenic oxide dissolved in water was added. Ayellow sol was obtained, dried, and then calcined at 200 C. overnight ina mufiie furnace.

The catalyst was broken into small particles, sieved and 200 ml. of 40 x100 mesh catalyst material was charged to a reactor. When tested at thesame conditions as in Example 1, with the single exception that thereaction temperature was 500 C., over 30 minutes of operation 2.2 g. ofacro'lein was obtained. This corresponds to a conversion of 13.8%, witha yield of 207%. Some acrylic acid was also formed during the reaction.

4 Example 4 A catalyst comprising 5.2% arsenic oxide and 41.6%dodecamolybdophosphoric acid on silica was prepared as describedhereinafter. To 825 g. of ammonia-stabilized 30% silica sol was added asolution containing 252 g. of dodecam-olylbdophospho-ric acid(hydra-ted), 150 ml. of distilled Water and 16 ml. of concentratednitric acid. Then 24.4 g. of arsenic oxide in 150 ml. of water was addedto the sol, and the preparation was heated and stirred on a hot plateuntil the sol had thickened. It was dried overnight in an oven at C.,and then calcined in a muflle furnace for 24 hours at 250 C. and 1.5hours at 450 C. After cooling, the catalyst was crushed, sieved, and ml.of 80 x 200 mesh catalyst material was charged to a laboratoryVycor-glass, fluid bed reactor.

To the react-or was fed a stream of 152 ml. of propylene and 925 ml. ofair per minute at STP. Reaction temperature was 428 C., and the contacttime was 2.2 seconds. Over 33 minutes of reaction 1.46 g. of acroleinwas obtained, corresponding to a conversion to acrolein of 11.6% with24.2% yield. Other products included a small amount of acetaldehyde, C0,C0 and organic acids. The total conversion to organic acids was 26.8%,with acrylic acid the major component.

Example 5 A catalyst comprising 5.2% arsenic oxide and 41.6%dodecamolybdophosphoric acid on silica was prepared as described inExample 4. The resulting catalyst was ground, sieved, and 145 ml. of thecatalyst of 80 x 200 mesh was charged to a fluid bed reactor.

A feed stream comprising 127 ml. of propylene and 952 ml. of air perminute, STP, was fed to the reactor. The reaction temperature was 428C., with 3.14 seconds contact time. After. 39 minutes of reaction, theproduct contained 1.65 g. of acrylic acid, 0.26 g. of acetic acid, and1.11 g. of acrolein. The conversion to acrylic acid was 10.4%, at 24.1%yield. The conversion to acetic acid was 2.0%. The conversion toaorolein was 9.0%, at 20.8% yield.

Example 6 The catalyst (145 ml. of 80 x 200 mesh) of Example 4 wastested at 445 C. and 2.16 seconds contact time. The feed comprised 180ml. of propylene and 1351 ml. of air per minute, STP. After 28 minutesof operation, the product contained 2.1 g. of acrylic acid, 0.5 g. ofacetic acid, and 0.98 g. of acrolein. The conversion to acrylic acid was12.9% at 27.5% yield. The conversion to acetic acid was 3.6%. Theconversion to acrolein was 7.7% at 16.5% yield.

Example 7 The catalyst (145 ml. of 80 x 200 mesh) of Example 4 wastested at 445 C. and 3.31 seconds contact time. The feed comprised 118ml. of propylene and 882 ml. of air per minute, STP. After 43 minutes ofoperation, the product contained 2.2 g. of acrylic acid, 0.48 g. ofacetic acid, and 1.15 g. of acrolein. The conversion to acrylic acid was13.6%, at 22.7% yield. The conversion to acetic acid was 5.8%. Theconversion to acrolein was 8.9%, at 14.9% yield.

Example 8 10 milliters of a catalyst comprising 5.2% arsenic oxide and41.6% dodecamolybdophosphoric acid on silica prepared as described inExample 4 and in the form of small granules was charged to a fixed bedmicrocatalytic reactor system. The system was connected to a gaschromatograph with appropriate gas sampling valves. This arrangementpermitted continuous operation of the reactor with sampling of theeffiuent from the reactor and quantitative analysis of the productstream as de ired. The feed stream contained isobutylene instead of thepropylene of the preceding examples. The results obtained are shown inTable 1. In addition to methacrolein, methacrylic acid and acetic acid,traces of acrolein and acrylic 3. A catalytic mixture in accordance withclaim 1 acid were also obtained. wherein the carrier is a silicacarrier.

TAB LE 1.--ISOBUTYLENE OXIDATION Methacrolein Methacrylic Acid AceticAcid Temp., Contact C4HsIOgZHzOZNz C. Time, sec. Mole Ratios Convn.,Yield, Convn., Yield, Convn., Yield, Percent Percent Percent PercentPercent Percent The results obtained when the catalyst compositions ofthe invention were used to prepare acrylonltrrle from 4. A catalyticmixture in accordance with claim 2 propylene, oxygen and ammonia are setforth in Table 2. wherein the carrier is a silica carrier. In the table,ACN stands for acrylonitrile, and MeCN 5. A catalytic calcined mixturein accordance with stands for acetonitrile. The catalyst employed inExclaim 1 consisting essentially of (l) 1 to percent by amples 9 to 14inclusive, comprised 5.2% AS205 and Weight of an oxide of arsenic, (2) 5to 60 percent by 41.6% H PMo O prepared as described in Example 3. 20weight of dodecamolybdophosphoric acid, and (3) a car- 200 ml. of x 100mesh catalyst material was employed rier as the remainder of themixture, wherein said oxide of in Examples '9 to 14, inclusive. arsenicand said dodecamolybdophosphoric acid are sup- The catalyst employed inExamples 15 to 22 inclusive, ported on said carrier. comprised 2.7%AS205 and 42.8% H PMo O prepared 6. A catalytic mixture in accordancewith claim 5 as described in Example 1. 200 ml. of 40 x 100 mesh 25wherein said oxide of arsenic is arsenic oxide. catalyst material wasemployed in Examples 15 to 22, 7. A catalytic mixture in accordance withclaim 6 inclusive. wherein the carrier is a silica carrier.

TABLE 2.CATALYTIC SYNTHESIS OF ACRYL ONITRILE FROM PROPYLENE, OXYGEN ANDAMMONIA Example Temp., Mole Ratios, GHSV, Convn. to Convn. to YieldYield Convn. Yield of No. C. C:Ha:O2:NI-Ia:H2O:Nz S.I.P. ACN, 011 AON,on of AGN, of ACN, to MeGN, MeCN,

C3116 NH3 on CaHa 011 NH:; on Cal-Is 0T1 CaHa :1. 521' 495 1:1. 5:1 72038.7 as. 7 57. 9 33.7 7. 7 11. 5 495 1=1. 5: 1: 900 34. 8 34. 8 55. 835. 6 6. 4 10.3 495 1:2: 1. 25: 720 33. 7 26.8 50.6 26. s a. 7 13. 1 4951211521 Z 530 39.0 35.0 55.9 sa'o 917 1418 495 1:1. 5: 1 720 35. 7 3s. 753. 5 30. 7 8.5 12. 4 490 1:1. 5:1 540 37.8 37.8 49.8 37. 3 9. s 12. 9435 1:2: 1. 25 530 30. 0 24. 2 33. 7 25. 4 7.8 10. 0 405 1:1. 5:1: 54025.0 25.0 53. 5 27.8 13. 3 1s. 5 455 1:2:1.25: 030 19.3 15.5 26.9 18.513.3 19.3 405 1:1 5:1: 540 28.4 28.4 39.2 30.9 14.7 20.3

e No water was fed in this example.

The calcining operations described herein were carried 8. A catalyticcalcined mixture containing: out in the presence of air. Percent byWeight The catalyst compositions of the invention have been (A) ArsenicOxide 5 2 illustrated with reference to certain representative catalyst(B) lybdophosphofic acid u 41 6 compositions. However, other catalystcompositions fall- (c) Silica 53 2 ing within the range of my catalystcompositions specified herein give generally similar results. While theoxide of arsenic employed in the catalyst compositions specificallydisclosed is arsenic oxide an equivalent amount of arsenous oxide can beused in place of arsenic oxide. 55

Both arsenic oxide and arsenous oxide appear to work equally well in theeatalysteompositions f the invention ous solution of arsenic oxide tothe aqueous mixture ob- The invention has been described in detail withparin 1, drying the mixture obtained 2 and ticular reference topreferred embodiments thereof, but calcllllng the dfleq mixtufeit willbe understood that variations and modifications 9- P 9 P accordance Wlth91mm 9 Wherem the can be ff t d Within the spirit and Scope f theinvencalcmatron 1s carned out at a temperature of from about tion asdescribed hereinbefore and as defined in the about aPPeIlded claimsReferences Cited and wherein said arsenic oxide and saiddodecamolybdophosphoric acid are supported on the silica.

9. A process of preparing a catalyst composition which comprises (1)adding an aqueous solution of dodccamolybdophosphoric acid to a silicasol, (2) adding an aque- Iclaim:

1. A catalytic calcined mixture consisting essentially UNITED STATESPATENTS of (1) 1 to 20 percent by weight of an oxide of arsenic,2,301,966 11/1942 Michel et a1 260683.15 (2) 5 to 60 percent by weightof a phosphomolybdic acid 2,450,675 10/ 1948 Marisic et al 252437 and(3) a carrier, wherein said oxide of arsenic and said 2,547,380 4/1951Fleck 252437 phosphomolybdic acid are supported on said carrier.2,798,890 7/1951 Waterman et a1. 260683.15

2. A catalytic calcined mixture consisting essentially 2,881,212 4/ 1959Idol et a1 252437 of 1 to 20 percent by weight of arsenic oxide, 5 to 503,190,913 6/1965 Fetterly et a1 252435 percent by weight of aphosphomolybdic acid and a carrier, wherein said arsenic oxide and saidphosphomolybdic DANIEL WYMAN "nary Examme' and are supported on saidcarrier. P. E. KONOPKA, Assistant Examiner.

1. A CATALYTIC CALCINED MIXTURE CONSISTING ESSENTIALLY OF (1) 1 TO 20PERCENT BY WEIGHT OF AN OXIDE OF ARSENIC, (2) 5 TO 60 PERCENT BY WEIGHTOF A PHOSPHOMOLYBDIC ACID AND (3) A CARRIER, WHEREIN SAID OXIDE OFARSENIC AND SAID PHOSPHOMOLYBDIC ACID ARE SUPPORTED ON SAID CARRIER.